Field emission devices and field emission electron emitters are known in the art. Typically, these prior art structures employ preferentially shaped electron emitters wherein an emitting tip/edge having a geometric discontinuity of small radius of curvature is formed. The desire for such a tip/edge feature is obviated by the need to provide for very strong electric field enhancement near the region of the electron emitter so that electrons may be extracted. In an attempt to increase the susceptibility to emit electrons techniques have been employed to provide work-function lowering materials, such as cesium, onto the surface of/directly into the bulk of electron emitters.
The need for emitting tips/edges with small radius of curvature imposes a restriction on repeatable realization of electron emitters. The technique of applying special materials to the surface of/in the bulk of emitters introduces operational instabilities due to the difficulty in maintaining the materials at/in the electron emitter.
Electron emitters of the prior art and field emission devices employing electron emitters of the prior art also suffer from damage incurred as a result of ion bombardment at the electron emitter. In the presence of very low residual gas pressures the emitters are still subjected to occasional ion attack which may damage the emitting tip/edge and render it useless.
Some other prior art field emission electron emitters do not employ tips/edges of small radius of curvature. However, such structures exhibit electron emission characteristics which impose significant limitations on emitter utility such as, for example, effectively controlling the emission current and emission trajectory.
Accordingly, there exists a need for a field emission device and a field emission electron emitter which overcomes at least some of the shortcomings of the prior art.